1. Field of the Invention
This invention relates to an adhesive silicone composition of the addition curing type, and more particularly to an adhesive silicone composition which can firmly bond with organic resins, especially polyamide resins, but is not adhesive to metals so that molded parts are improved in mold release.
2. Prior Art
Several methods are known for bonding addition curing type silicone elastomers to thermoplastic resins. One known method involves applying a primer to a surface of thermoplastic resin, applying and curing an uncured silicone elastomer composition thereto. In another method, a self-tack silicone elastomer composition is directly applied and cured to a thermoplastic resin. Since the former method, however, requires the step of applying the primer to a molded part of thermoplastic resin, it is time consuming and complicated in equipment and process. The latter method suffers from the drawback that the self-tack silicone elastomer composition itself sticks to a metal mold.
Under the circumstances, we proposed in JP-A 172738/1994 corresponding to U.S. Pat. No. 5,405,896 a method for bonding to a thermoplastic resin an adhesive silicone elastomer composition containing an organic silicon compound having an aromatic ring as a tackifier. Since this adhesive silicone elastomer composition does not bond to metals, but self bonds to various thermoplastic resins, it becomes possible to directly apply and cure this composition to molded parts of thermoplastic resin without a need for a primer.
The above adhesive silicone elastomer composition, however, is still unsatisfactory in adhesion to polyamide resins which are typical engineering plastics. A further improvement in adhesion is desired.
Therefore, an object of the invention is to provide an adhesive silicone composition which can establish firm bonds with organic resins, especially nitrogenous organic resins, typically polyamide resins, but is less adhesive to metals so that when molded parts are prepared using metal molds, the molded parts can be readily removed from the molds.